Place the annatto, cumin, peppercorns, allspice, and cloves in a spice grinder and process to a fine powder. (You can use an electric coffee grinder for the spices, but it will not be suitable for coffee afterwards.)

Remove the seeds and veins from the habanero chiles and chop coarsely. (If you want a hotter dish, leave some of the veins and seeds in. If you want a milder dish, substitute a milder chile.)

Process the orange juice, vinegar, chiles, salt, garlic, and the powder you made in step 1 in a blender or food processor until liquefied. Add the lemon juice and tequila.

Cut the pork into 2 inch (5 cm) chunks. Leave the fat on the meat, to keep the pork moist while roasting; you can remove it after cooking if you wish. Place in a large, self-sealing plastic bag with the marinade. Seal bag and turn to evenly coat the meat. Refrigerate for 8 to 24 hours, turning occasionally.

Heat oven to 325° F (160° C). Dump the meat and the marinade in a roasting pan lined with banana leaves or foil, making sure to wrap tightly so no steam escapes. If using banana leaves, an outer wrapping with foil will help seal in the steam. Cook for 4 hours. Open packet carefully; the meat should shred easily with a fork.